How to Convert GPT to MBR or Convert MBR to GPT without Losing Data?

January 31, 2019

This paper gives a brief introduction of MBR and GPT and tells you how to make conversion between GPT and MBR disk without data loss via AOMEI Partition Assistant.


About MBR and GPT Disk

MBR - Master Boot Record: it is a guide sector in the very front of drive. It was named in 1983 when partitioning the hard disk or flash disk of IBM compatible personal computer. At that time, PC DOS 2.0 was able to support hard disk. MBR describes the information of logical, including file system and organization type. Besides, MBR also contains the executable code produced when computer loads operating system in the second stage of start or the boot record connecting every partition (VBR). Such MBR is usually called boot routine.

Note: MBR cannot exist in a media which cannot be partitioned, such as soft disk.

GPT - GUID (Globally Unique Identifiers) Partition Table: it is a new standard of disk partition table originating from EFI (Extensive Firmware Interface). Compared with MBR, it provides a more flexible disk partition principle.

  • What are the limitations of MBR disk?

  1. MBR disks only support up to 2TB partition size and support four primary partitions only. If partition size surpasses 2TB, the rest space will show as unallocated space.

  2. If more partitions are needed, you have to build a secondary structure known as extended partition, and then you can create logical partitions.

  3. MBR partitioning rules are complex and poorly specified.

  • What are the advantages of GPT disk?

  1. It can make full use of a very large size to break the 2TB limit of MBR disks.

  2. GPT disks allow an almost unlimited number of partitions. Though Windows implementation restricts the number to 128, it is completely sufficient for using.

  3. Each GPT partition has a unique identification GUID and a partition content type. And you can have more primary partitions.

  4. There nearly isn’t any limitation to the size of partition. The sector is numbered by a 64-bit integer. A partition with such number of sectors, can it be small?

  5. Partition on GPT disk has self-contained backup which is stored on the end of the disk while the original one is saved on the start. When one of the two is destroyed, you can restore it with the other.

  6. Every partition on GPT disk can have a name which is different from partition label.

When Need to Convert MBR/GPT Disk?

  • As mentioned above, MBR disks only support up to 2TB partition size, so if you have a disk which is MBR formatted and larger than 2TB, you could only use 2TB disk size among it, but the reset of it could not be used. Converting MBR disk to GPT disk is necessary to make full use of the disk space.

  • On the other hand, since Windows 95/98/ME, Windows NT4, Windows 2000, Windows 2003 32-bit, or Windows XP 32-bit version does not support GPT partitions, a GPT disk will display as GPT protective partition in these systems, thus you could not access the data until you convert it back to MBR disk. In such situation, you have nothing to do but to convert GPT to MBR disk.

Note: if you want to convert any larger than 2TB GPT disk back to MBR disk, you'd better ensure that the data does not account for space more than 2TB. Otherwise, the overloaded data will get lost. However, if you really want to convert your GPT drive on which there are more than 2TB data into MBR disk, you can transfer the extra data to other place via a data migration software before your conversion.

How to convert disk between GPT and MBR without affecting OS?

First, To convert GPT to MBR or MBR to disk without data loss, you can apply AOMEI Partition Assistant Professional. Let’s see how it works.

Step 1. Install and launch AOMEI Partition Assistant Professional. Select the data disk you want to convert and right click it, and then select "Convert to GPT Disk" (or Convert to MBR Disk) in the drop-down menu.

Convert Data Disk to GPT

PS.: If you are working with Windows Server, you can apply AOMEI Partitioni Asssitant Server or advanced edition.

Step 2. Click "OK" after confirming the operation.

OK to GPT Data Disk

Step 3. You can preview the conversion. To save the change, please click "Apply" on the toolbar and wait for process to complete.

Apply to GPT Data Disk

How to convert GPT to MBR without operating system?

When installing Windows 10/8/7, you may get an error saying that Windows cannot be installed to this disk: The selected disk has an MBR partition table or GPT partition table. In that case, you can convert disk between MBR and GPT before installing Windows. You can use a USB flash drive or CD to create an AOMEI Partition Assistant bootable media to convert to MBR/GPT without data loss. Refer to the steps listed below:

Step 1. Insert an USB flash drive or CD to another working computer running Windows 10/8/7, and launch AOMEI Partition Assistant.

Step 2. Click on "Make Bootable Media "and follow the wizard to finish creating a bootable media.

Make Bootable Media

Step 3. Insert this bootable disk to the computer that you’re having problem installing Windows on, and then boot it from this bootable media.

Step 4. When the interface of AOMEI Partition Assistant is loaded, you can convert the hard drive to MBR or GPT.

After that, you should be able to install Windows on this disk. If data loss is not an issue, you can convert MBR to GPT with DiskPart utility.


  • For conversion between MBR and GPT disks on Laptop, please make sure the power supply is sufficient

  • To ensure the data is consistent, do not abnormally terminate the program during the conversion process.